forest vs sylva

forest and sylva both are nouns.

Word	Noun	Adjective	Verb	Adverb
forest	Yes	No	Yes	No
sylva	Yes	No	No	No

As nouns, sylva is a hyponym of forest; that is, sylva is a word with a more specific, narrower meaning than forest:

Other hyponyms of forest include greenwood, riparian forest, silva, tree farm.

forest (noun)	sylva (noun)
the trees and other plants in a large densely wooded area	the forest trees growing in a country or region
land that is covered with trees and shrubs

forest (verb)	sylva (verb)
establish a forest on previously unforested land